This invention relates to an exposure apparatus, and more particularly to an exposure apparatus for use in a copying apparatus.
Generally, a copying apparatus equipped with an exposure apparatus having an automatic belt-type document feeding mechanism is used to copy a sheet-like document without expending a large amount of time and labor. This document feeding mechanism is designed to automatically carry the document to an exposure region along an exposure table and a belt-like cover, keeping the document in place.
In a prior art exposure apparatus provided with such an automatic belt-type document feeding mechanism, when the document reaches a position immediately before a forward end portion of the exposure region, that is, when the document is carried with some delay, the lights irradiated onto this forward end portion are allowed to illuminate that portion of the carrying belt which is located above the forward end portion. Although this type of carrying belt is generally colored white, it begins to stain as the frequency of its use is increased. The prior art exposure apparatus, therefore, has a drawback in that the stained portions of the carrying belt are projected onto a copy paper to blur the same. In the prior art, therefore, a white colored mask member is provided at the forward end portion of the exposure table so as to prevent the carrying belt from being copied. With such a construction, even when the document is carried with some delay, the white colored face of the mask member was copied onto the copy paper, thereby preventing the carrying belt from being copied.
This type of prior art exposure apparatus is shown in FIG. 1. In the prior art exposure apparatus 10, beneath a forward end portion of an underside 14 of a loading board 12 to be loaded with document 22 thereon a white colored mask plate 16 is mounted parallel to the loading board 12. This mask plate 16 is disposed so that it may shield the lights projected onto a forward end portion V of the exposure region and so that its white colored face H may be exposed at all times in place of such forward end portion V of the exposure region.
However, when a main body 17 is moved in a direction indicated by the arrow T and the document 22 is thereby exposed sequentially from an adjoining portion PW of the document 22 to a forward end portion PV thereof, a shadow of the mask plate 16 is produced in a portion W of the exposure region, as shown in FIG. 1, with the result that a difference in quantity of light is produced between the lights directed toward the portion S of the exposure region and those directed toward the portion W thereof. That is, the portion S of the exposure region is projected with first light beams emitted from a lamp 18 and reflected from a first reflector 20 as well as second light beams irradiated from a second reflector 21. However, the portion W of the exposure region is projected only with the first light beams, said second light beams being shielded by the mask plate 16. The light beams reflected from the portions PS and PW of the document 22 are guided, through a mirror 24, to a photosensitive member (not shown). Particularly where the quantity of light for exposure is decreased in some cases by being adjusted in accordance with the density of the document 22 and in other cases by production of a stain on the exposure lamp, a difference in the quantity of exposure lights between the portions S and W appears as a density difference (CS and CW indicated on a copy paper 26).
That is, where the prior art exposure apparatus 10 is used, copying the document 22 shown in FIG. 2 disadvantageously results in the formation, on the copy paper 26, of such a blurred copy image as shown in FIG. 3.